1. Field of the Invention
This invention relates generally to the measurement of the parameters of gears and, more particularly, to apparatus and procedures for verifying parameters of an involute axle gear. The apparatus of the present invention is adapted to be portable, permitting the axle gear parameters to be measured at remote locations.
2. Description of the Related Art
The use of gears to transfer rotational motion from one shaft to another shaft is well-known in modern industrial practice. One type of gear is the involute gear or pinion, a gear configuration that has been widely used in the railroad industry. The involute gear is especially desirable in those applications where the center of the gear or pinion can not be maintained with precision.
In the fabrication of the gear, maintaining of precise tolerances is essential. Otherwise, the gear or pinion can develop excessive wear and can be unsuitable for operation after an unacceptably short period of time. Furthermore, the size and operational position of the gears typically increase the difficulty in exchanging a defective gear for a suitable gear. Thus, the user of a gear or pinion will typically want to verify that the measurements of the gear parameters are within specified tolerances, even during routine maintenance. Similarly, it is frequently desirable to measure the gear or pinion after extended use. Unacceptable departures from the original profile can identify design problems in the apparatus utilizing the gear or pinion or defective workmanship or defective materials in the fabrication of the gear.
At present, complex automatic apparatus is available for testing and verifying the parameters of involute gears and pinions. The automatic apparatus involves the use of fulcrum points, linkage apparatus and ratio arms. While this apparatus provides acceptable testing and verification of the gear or pinion parameters, the apparatus is expensive and requires trained personnel for its operation. In addition, the testing apparatus of the prior art requires that the gear be brought to the site having the test apparatus.
Apparatus for testing the parameters of involute gears and pinions, which overcomes many of the problems of the prior art and the related art, has been described in U.S. Pat. No. 4,962,590. Disks are concentrically coupled to the gears and pinions to be tested, the disks having surfaces which have a radius from the axis of the gear equal to the base circle radius. The disks are rolled on tracks, the tracks having a displacement measuring probe for contacting the gear teeth in the plane of the tracks. The contact point is therefore positioned on a tangent line to the gear base circle when the disks (coupled to the gear) are rotated on the tracks. As explained in the referenced U.S. Patent, a correctly configured involute gear surface will pass through a fixed point on a line tangent to the base circle when the disks coupled to the gear travel on the tracks. That is, a probe tangent to the base circle and in contact with an involute gear tooth surface should show no displacement when the base circle disks coupled to the gear travel without slipping on the tracks. 1n this manner, selected parameters of the involute gear or pinion can be measured and/or verified.
The apparatus of the referenced U.S. Patent, while theoretically capable of operation with any gears of any size, becomes impractical for large gears. The disks which are coupled to the gear become heavier and more awkward as the size of the gear increases. Furthermore, the increase in size of the gears themselves make the handling of the gears more difficult.
A need has therefore been felt for apparatus for verifying the parameters of an involute gear that is relatively inexpensive to manufacture, is simple to operate, which can be easily transported to remote locations to perform the measurements in the vicinity of the machines using the involute gear, and which does not require substantial manipulation of the gear being tested.